We propose to continue the ongoing investigations of the biochemistry of bacterial membrane-related processes about which we have published extensively in the last 5 years. Mutants and especially those in Escherichia coli K-12 provide the primary tool for physiological and biochemical studies. In addition, other bacterial species including plasmid-containing strains of Pseudomonas aeruginosa and Staphylococcus aureus will be used. The phenomena to be studied in the next year include: (a) cation transport systems for calcium, magnesium and manganese; b) the enzymatic basis for mercury and organomercurial resistance determined by genes on bacterial plasmids; and (c) the mechanism of plasmid-determined resistance to cadmium. The cation transport studies will emphasize the energy-input and coupling of energy to calcium transport in everted and normal-orientation membranes and subcellular membranes from photosynthetic bacteria. The manganese transport chelate which we found in Bacillus subtilis will be purified; and the involvement of the manganese transport system of S. aureus in cadmium sensitivity and resistance will be pursued with subcellular membranes and with mutants. Final purification of the mercury reductase and additional enzyme(s) involved with organomercurial degradation is a goal for the year.